It happened around 5:30 p.m. Thursday on the 2100 of West Lehigh Avenue.
Police say a 20-year-old McDonald's employee was involved in an altercation with two customers when she was stabbed once in the left arm.
The employee was transported to an area hospital where she's listed in stable condition.
Police are looking for the two customers at this time.
It's unclear what sparked the altercation.
Anyone with any information is asked to call police at 215-686-TIPS.